I. Field of the Invention
The present invention generally relates to a cable modem system comprising a mechanism which dynamically assigns an Internet protocol (IP) address in response to a client request. More particularly, the present invention relates to a cable modem system in which an IP address-assigning mechanism assigns a private address and a global address according to a classification of a requesting client.
II. Background and Material Information
Cable modem systems, which enable digital communication over a coaxial cable network for cable television (CATV), have recently become widespread. The cable modem system realizes high-speed computer communication using the same signal that a regular television system uses, i.e., a radio frequency (RF) signal. In the cable modem system, both television service and digital communication service can be provided to a member via the same cable.
FIG. 3 is an exemplary block diagram showing the configuration of a cable modem system. FIG. 4 is an exemplary block diagram showing the configuration of a cable modem (CM). FIG. 5 is showing exemplary communication between two CMs connected to the same cable.
As shown in FIG. 3, a cable modem system mainly comprises a cable modem terminate system (CMTS) 302, a CM 304, and a CATV cable 306 via which CMTS 302 and CM 304 are connected to each other. CMTS 302 receives data from a provider""s network 308, which conforms to a standard for local area networks (LAN) such as 100BASE-T or asynchronous transfer mode (ATM), and transforms the data into an RF signal and vice versa. CM 304 is generally located at a home, for instance, to realize a small office/home office (SOHO). CM 304 is connected to a user computer such as personal computer or workstation (PC/WS) 310 via a user""s network 312 conforming to a standard such as 10BASE-T or 100BASE-T.
CMTS 302 and CM 304 enable unsymmetrical high-speed communication in the cable modem system, i.e., communication from CMTS 302 to CM 304 (hereinafter referred to as xe2x80x9cdownstream communicationxe2x80x9d) at a predetermined rate, e.g., 10 Mbps-40 Mbps and communication from CM 304 to CMTS 302 (hereinafter referred to as xe2x80x9cupstream communicationxe2x80x9d) at a predetermined rate, e.g., 1 Mbps-10 Mbps. A plurality of CMs 304a-304b connected to single CATV cable 306 share both the downstream frequency (F1) and the upstream frequency (F2) on CATV cable 306.
As shown in FIG. 4, CM 304a comprises an RF receiver 402 and an RF transmitter 404. CM 304a assists PC/WS 310a in communicating with another user computer 310c connected to another CM 304b, however, CM 304a can not receive an RF signal directly from CM 304b because of the difference in frequencies between the downstream communication and the upstream communication.
Therefore, as shown in FIG.5, CMTS 302 comprises a relay unit 502 which receives a data frame sent from CM 304a and sends it to another CM 304c. Relay unit 502 enables the CATV cable 306 to be treated in the same way as an ethernet LAN and allows the application of techniques used for a regular LAN.
Originally, CM 304 just needed a media access control (MAC) address and did not need an IP address. However, recently, even a hub or a modem has become a mechanism conforming to a network management protocol such as simple network management protocol (SNMP), which requires an IP address, so that a provider""s SNMP server can grasp conditions of the hub or the modem and alter their definition information.
Single CM 304 is usually supposed to be assigned to single user. For an operator to manually assign those IP addresses would be a hard task. Therefore, a mechanism conforming to a dynamic host configuration protocol (DHCP) is usually used. A server which comprises the mechanism is called DHCP servers and it dynamically assigns an IP address to a client, such as CM 304 or PC/WS 310, in response to a request from the client.
In the case of a huge cable modem system, the number of CMs 304 is very large, e.g., thousands through ten thousands. Moreover, because CM 304 is usually kept working without being shut off the power, many IP addresses are capable of being held by most CM 304s. Therefore, more IP addresses are required so that the system can efficiently work in this situation.
However, the number of IP addresses is limited and an exhaustion of IP addresses has turned into a grave issue. Therefore, it is difficult to own many IP addresses and costly for a company.
An IP address for accessing to the Internet is also called a xe2x80x9cglobal addressxe2x80x9d. Originally, an xe2x80x9cIP addressxe2x80x9d meant an address used in an IP network, one of which is the Internet. However, xe2x80x9cIP addressxe2x80x9d is now often used to mean just an address used for the Internet. To avoid confusion, an IP address for accessing to Internet will be referred as to xe2x80x9cglobal addressxe2x80x9d and an IP address other than a xe2x80x9cglobal addressxe2x80x9d will be referred to as a xe2x80x9cprivate addressxe2x80x9d in the following.
In view of the foregoing, the present invention is directed to a system and method for managing an assignment of IP addresses in a cable modem system that substantially obviates one or more of the problems due to limitations and disadvantages of the past approaches.
In accordance with an aspect of the present invention, as embodied and broadly described, the present invention is directed to a cable modem system. The system comprises at least one cable modem, at least one user computer connected to the cable modem, a CMTS, a cable via which the cable modem and the CMTS are connected, and means connected to the CMTS for assigning an IP address of a specific kind according to the classification of a client in response to a request for an IP address from the client.
In accordance with another aspect of the present invention, there is provided a method for managing an assignment of IP addresses in a cable modem system. The method comprises issuing a request for an IP address by a client and issuing an IP address of a specific kind according to the classification of the client by a server.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. Further features and/or variations may be provided in addition to those set forth herein. For example, the present invention may be directed to various combinations and subcombinations of the disclosed features and/or combinations and subcombinations of several further features disclosed below in the detailed description.